Control system



C. B. COCHRAN CONTROL SYSTEM Dec. 8, 1964 7 Sheets-Sheet 1 Filed Aug. 23, 1963 I no enter Clement B-Cochran. 5a ZlfaZ/ue, Wand Dmw fl-bborneufi Dec. 8, 1964 c. B. COCHRAN 3,160,321

CONTROL SYSTEM Filed Aug. 2-3, 1963 7 Sheets-Sheet 2 Invent r Clement B. Cochran aHcborrzegs Dec. 8, 1964 c. B. COCHRAN 3,150,321

CONTROL SYSTEM Filed Aug. 23, 1963 7 Sheets-Sheet 3 Egg 5 37 6O Inn/anion" Clemenl: .B.Cocbran. 3:2 Wzflm,Wawa/Dmw .flttomegfi Dec. 8, 1964 c. B. COCHRAN 3,160,321

CONTROL SYSTEM Filed Aug. 23, 1963 7 Sheets-Sheet 4 led an us 5| VALVE f TIMER T ACTUATOR 2 sun-con 551455 I VALVE Z] T ACTUATOR Tl VALVE MER ACTUATOR 52 L "Z C0 N TROL r F TIMER --1 VALVE 524 I ACTUATOR I VALVE F sense L 2,2 m 2 ACTUATOR M l VALVE Tl ER ACIUATOR 52-2 k u N rr 5l-3 r vALvs 1/ 53-3 F TIMER T ACIOATOR f STATKOH SENSE L 5 l van/E Z3 4 r ACt'UATOR VALVE ll4 TMER ACIUATOR Pmrownou KW 52 CONTROL V Y To omen s'm'uons Inventor 24-27 Clenzgtil: 5. Cochrqq.

8% Wa la H-t'tornegs Dec. 8, 1964 c. B. COCHRAN 3,160,321

CONTROL SYSTEM Filed Aug. 25, 1963 7 Sheets-Sheet 6 I (.5! MINIMUM VALVE TIMER Ac'rumm FIRST 5 MAXIMUM PRooucT f TIMER V MIN M M 52 N SENSE CONTROL VALVE g 313 ACTUATOR I MINIMUM E TIMER f H I I MAfiIMUM vaooucr TIMER 'Ac'ruAroR RATIO J CONTROL 313 (Connects 5| 2 TO ALL MINIMUM k snsss) HMER VALVE I: ACTUATOR I) 312-27 N 3:9 2 BIG N TIMER I SECOND [52 2 t PRODUCT Q SENSE 31332 f, MNMUM VALVE ACTUAT L45 2 MNMDM I r CONTROL R E TIMER MAXHVWM VALVE TIMER ACTUATOR V I II I I To STATlONS 24 -27 Inventor Clement B.Cochran 35/- ZJallaa. 'Dnw Dec. 8, 1964 c. B. COCHRAN 3,160,321

CONTROL SYSTEM Filed Aug. 23, 1963 7 Sheets-Sheet 7 FROM ALL nRsT-PRooucT F Ml N\MUM TIMERS MIN. 32 I I Y w L i T 'CLUTCHES ALL FlRST PRODUCT 'TIMERS cLvTcuES ALL sicouo PRODUCT TIMER-5 I l FROM ALL '-ji SECOND-PRODUCT MINIMUM 352 313 TlMERs Inventor Clement B.Cochr'an United States Patent 3,160,321 CQNTRQL SYSTEM Clement B. Cochran, Des Moines, Iowa, assignor to Eagle Iron Works, Des Moines, Iowa, a corporation of Iowa Filed Aug. 23, 1963,Ser. No. sa4,727 19Ciainrs. (Cl. 222-64) This invention relates to a new and improved control system for sand classifying apparatus and the like and more particularly to a new and improved control system for a water scalping tank employed in the classification of sand or other granular material. This is a continuation in-part of application Serial No. 140,914, filed September 26, 1961, now abandoned.

A typical water scalping tank utilized for classification of sand or other watereinsoluble granular material comprises an elongated tank into which a slurry of sand and water is introduced. The sand and water mixture flows into one end of the tank and a water overflow occurs I at the opposite end of the tank. The sand settles to the bottom of the tank, the larger sand particles settling near the feed end with progressively finer particles settling toward the overflow end of the tank. Sand outlets are located periodically along the bottom of the tank and are employed to discharge the various sizes of sand as they accumulate at the bottom of the tank. The sand is permitted to accumulate to a definite depth at each outlet. By bleeding off the sand through the outlets at the bottom of the tank at approximately the same rate as it accumulates, it is possible to utilize the sand to seal off the water from the outlet openings. Accordingly, only wet sand is discharged from the outlet openings at the bottom of the tank and substantially clear water overflows from the top of the tank. The

various outlets at the bottom of the tank discharge different grades of sand and these are flumed away by one or more longitudinal flumes. By controlling the discharge from the outlet openings to the flurnes, the gradation of sand in the flumes can be controlled to meet particular specifications.

It is thus seen that the water scalping tank serves two basic functions. One is to remove excess water and thereby concentrate or thicken the sand. The second function is to segregate or classify sand into various sizes. These difierent sand sizes are then reblended in predetermined amount to meet definite specifications. Surplus sand of various sizes may be st-ockpiled or diverted to waste. In some applications, two or more specification materials may be produced using the same scalpin-g tank. Ideally, the tank would separate the sand into a plurality of non-overlapping sizes. In actual practice, there is an overlapping of the several sand sizes but sufiicient concentration of individual sizes is accomplished to enable the control of classification within the desired specifications.

To control the composition of a given specification sand, the amounts of sand discharged from the various outlet openings in the bottom of the scalping tank must be regulated relative to each other. This control may take the form of splitter gates or the like which are adjusted to afiord the desired composition in the specification sand. However, if the composition of the input sand or slurry changes substantially, it may be necessary to change the'setting of the control devices rather frequently in order to keep the specification material within the required limits. In many installations, it may be necessary to re-check the composition of the specification sand and to adjust the outlet valve controls as frequently as every hour. This is a time-consuming and, in many instances, quite wasteful operation.

It is an object of the present invention, therefore, to efiectively eliminate or minimize the effect of changes 'ice in the composition of the input sand or other granular material to a classifying apparatus such as a Scalping tank.

A particular object of the invention is to avoid the necessity for continuous sampling of the output sand in a scalping tank utilized for "the classificationand preparation of sand in accordance with apredeterminedspecification.

Another object of the invention is to avoid relatively large losses of useful sand or other granular material which might otherwise occur, in thejoperation of a scalping tank or similar classifying apparatus, due to relatively minor changes in the composition of the input to the apparatus. Aparticul'ar feature of thejinve'ntion is the utilization of a timing'apparatus, comprising motordriven time delay relays or other timers, toefiect this purpose.

An additional object of the invention is to afford an effective and convenientm'eans for regulating the sensitivity, relative to changes in the'cor'nposition of input material, of an automatic control system for a 'scalping tank or similar classifying apparatusfor granular materi a1- Another object of the invention is to provide a new and improved'contr-ol system that makes it' possible and practical to formulate 'two or more-specification sands, regardless of dissimilarities in the "specifications, in a single cycle of operation of a scalpingtahk orsirnilar classifying apparatus. A relatedobject er the invention is to control the relative amounts of 'two' or more specification products formulated substantially simultaneously by a single classifying apparatus such as a Water scalping tank.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show preferred fembodiments of the present invention and the principles thereof and what is now considered to 'be the best mode contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be made as desired by those skilled in the art without'departing from the present invention and the purview of the appended claims.

In the drawings:

FIG. 1 is a plan view of a water scalping tank in which a control system constructed in accordance with one embodiment of the present invention is incorporated, a part of the tank structure being cut away to show internal construction;

FIG. 2 is a sectional elevation view taken approximately along line 22 inFIG. 1; i

FIG. 3 is a detail plan view of a part of the control system for the water scalping tank of FIG. 1, but drawn to a somewhat larger scale;

FIG. 4 is a longitudinal elevation view taken approximately along line 44 in FIG. 1;

FIG. 5 is a detail sectional elevation view taken approximately as indicated by line 5-5 in FIG. 1, (but drawn to a substantially enlarged scale as compared with FIG. 1;

FIG. 6 is a block diagram of a control system for the scalping tank of FIGS. 1-5, constructed inaccordance with one embodiment of the invention;

FIG. 7 is a detail schematic diagram of one form of. electrical control apparatus for the system ofFIGQ 6;

FIG. 8 is a block diagram of a control system in accordance with another embodiment of .the invention; and

FIG. 9 is a detail schematic diagram of a part of the control system of FIG, 8.

FIGS. 1-4 illustrate the basic operating mechanism for a water seal-ping tank It) in which a control system con- Z structed in accordance with corporated. The scalping tank includes a basic tank structure comprising an input or coarse sand section 11 and an output or fine sand section 12, these two tank sections being joined together to afford a complete tank structure. At the left-hand end of the tank 10, as seen in FIGS. 1 and 4, there is located a feed box 13 to which an input conduit 14 may be connected. The feed box 13 is provided with an outlet opening 15 affording access to the interior of the tank section 11. It may also be desirable to provide an auxiliary water inlet at the input side of the tank. In FIG. 4, the water inlet 16 is located near the bottom of the tank section 11 below the feed box 13.

There are seven sand discharge outlet stations in the scalping tank 10, as best shown in FIGS. 1 and 4. These sand outlet stations are generally identified by the reference characters 21 through 27. The outlet station 21 is located nearest to the inletor feed box 13 and the discharge station 27 is located at the opposite orright-hand end of the tank. Thus, the discharge station 27. is the closest to the overflow conduit 28 from which the water flows on discharge from the tank 10. The sands discharged by the stations 21 through 27 are progressively finer, due to the classifying operation of the scalping tank, as described in greater detail hereinafter.

,FIGS. 2 and 3 illustrate the construction of one of the discharge stations, in this instance the initial discharge station 21., stationsare substantially similar in construction, the apparatus illustrated in connection with'the station'Zl in FIGS. 2 and 3 may be considered to'be typical of all of the sand outlet stations.

As shown in FIGS. 1-3, the sanddischarge station 21 comprises an upper frame including two transverse frame members 31 and 32 supported upon end posts 33 and 34 that are suitably mounted upon an internal section 35 of the tank 10. A mounting plate 36 bridges the central portion of the frame 31-34. This mounting plate affords a support for a paddle motor 37 having a switch arm 38 connected thereto. A motor shaft is also connected to a depending paddle rod 39 that carries a paddle member 41 located near the bottom of the tank as shown in FIG. 2. The upper portion of the paddle rod 39 may be encompassed in a guard 42 to protect the operating mechanism of the paddle and the motor 37 against contact with the water flowing through the tank, as described in greater detail hereinafter in connection with PEG. 5. The switch arm 38 (FIG. 3) is maintained in an initial or unactuated position by suitable means such as a spring 4 3 that is connected from the switch arm to a bracket 44. mounted upon the plate 36. Rotation of the switch arm 38, howthe present invention is in- I Since all of the sand outlets or discharge .7

watering screw to remove excess moisture, from which the sand is discharged to a conveyor apparatus for transportation to a given discharge location or stock pile, depending upon the requirements of the installation in which the scalping tank it) is employed. Since apparatus of this kind is conventional, it has not been illustrated in the drawings.

As noted above, the individual valve actuators 51, 52 and 53 are hydraulic devices that are solenoid operated. The hydraulic supply for the'valve actuators comprises a w puinp'75 (FIG. 1) that is driven by an electrical motor 7d. The pump assembly '75 may include the usual reservoir and suitable cut-elf and bleeder valves. The pump is connected to the valves 51, 52 and 53 by a pressure conduit or output line 77 and by a return line '78. The

' one pump '75 is used to operate all of the valve actuators The basic operation of the scalping tank 10 proceeds as follows. A'mixture of sand and water is fed into the feed box 13 through the conduit 14*(FIGS. l and 4) and into the scalping tank. At the same time, an auxiliary flow of Water may be supplied to the tank through the conduit 16. As the mixture flows out of the opening 15, the heavier particles tend to settle almost immediately in the neighborhood of the outlet station 21. Finer particles settle, progressively, in the areas adjacent the sand outlet stations 22-27. With the inflow of sand mixture and water properly adjusted, by adjustment of the input through conduit 16, virtually all of the sand settles by the time the water reaches the end of thetank, and the overflow of water into the conduit 28 is relatively clear and free of sand.

When the tank is placedin operation, all of the paddle motors such'as the motor 37 (FIG. 3) are energized.

ever,.as described hereinafter, can be effected to bring thev switch arm into contact with a sensing switch 45 that is also mounted upon the plate 36.

The mounting'plate Qdalso carries three solenoid operated hydraultic valves 51, 52 and 53. The solenoid operated valves 51, 52 and 53 are connected by suitable These motors rotate the paddles relatively freely in the water. in each instance, the switch arm 38, which is mounted on the motor'housing, is held out of contact with the sensing switch 45 by the spring 43. In this position of the arm 3%, the switch 45 is open. With all of these switches open, all of the valves controlling the outlet from the stations 21-27 are held closed'and a buildup of sand is initiated in the bottom of the scalping tank 10.

With particular reference to the sand discharge station Zll, as illustrated in F IG. 2, the sand 81 eventually accumulates to a level where it interferes with rotation of the paddle ll. When this happens, the stator oi the motor 37 tends to rotate about its shaft. The'inotor turns, against the spring 43, and pivots the arm 33 into engagement with the sensing switch 45. As a consequence, one, two or three of the valve operating cylinders 53-66 are 'actuated'by the solenoid operated control valves 51, 52

and 53 respectively. Consequently, the related discharge is sufiicient to indicatethat the valves 61-63 are opened and closed by verticalmovernent of the corresponding valve rods -57. v a

The valves 61, 62 and 63 open into three individual sand the sand mixtureoutletsTl-Tli may be connected to a de} V valve or Valves of the group 61-53 are opened, releasing sand into one or more of the flumes 65-67.

The discharge of sand into the flumes reduces the level within the scalping. tank,.in the areaadjacent tothe discharge station Zljand. eventuallyfrees the paddle 4-1 for con tinued rotation.

As soon as the paddle 41 is able to rotate freely, the spring 43 operates to turn the motor 37 and the switcharm 33 again out of engagement with the sensing switch 45. This is effective to actuate the s0lenoid 'controlled valves 51-53 and thereby cause the hydraulic valve lifters 58-60 to close the sand outlet valves. This process continues throughout operation of the scalpin'g tankltl, the control system of the present invention affording selective control of the valves to provide for the accumulation of sand of given constituency in the -ilumes 65-67 as described in greater detail hereinafter in connection with FIGS. 5-7., Of course, this mode of operation requires the use of motors capable of sustained periods of stalled operation without overheating.

FIG. 5 illustrates in substantial detail the mechanical construction for the sand discharge station 21. As shown therein, the paddle motor 37 is connected to a spindle assembly 82 supported by suitable thrust bearings, such as the ball bearings 83, in a sleeve 84 that is mounted upon the mounting plate 36. The sleeve 84 comprises an upward extension of the depending paddle rod guard 42. The lower end of the spindle assembly 82 is connected to the paddle rod 39 by suitable means, a pin connection being shown.

Also as shown in FIG. 5, the piston rod 86 for the valve operating cylinder 58 carries, at its lower end, a yoke 87. The lower end of the yoke 37 comprises a threaded collar 88 into which the upper end of the valve rod 55 is threaded. A suitable lock nut 89 is utilized to maintain the rod 55 in fixed position within the collar portion 88 ofthe yoke once the desired adjustment of the length of the rod has been achieved. The resulting connection between the cylinder rod 86 and the valve rod 55 provides for convenient and effective adjustment of the length of the valve rod to assure effective closing of the valve. It also permits some minor misalignment be tween the operating cylinder 58 and the valve 61, reducing the critical nature of mounting of the valve operating device 58 with respect to the valve itself.

The structure of the valve 61, in the illustrated embodiment, includes a valve guide and seat member )2 that is fixedly mounted on the bottom 90 of the tank. The valve guide and seat includes a re-entrant flange portion 92 that affords the actual valve seat. This flange 92 encompasses a relatively large central opening 93 in the casting comprising the member 21. The lower end of the valve rod 55 carries a valve disc 94, the valve disc having a seal member 95 mounted upon the upper surface thereof in position to engage the seating flange 92 of the member 91. The mounting of the valve disc 94 on the rod 55 entails the use of a threaded lower end on the valve rod, which eXtends through the valve disc, suitable nuts 96 being used to complete the mounting. Preferably, a protective sleeve 97 encompasses a portion of the valve rod 55 above the valve disc to protect it against abrasion from the sand 81.

FIG. 6 is a generalized block diagram of a control system for the scalping tank 10 that is constructed in ac cordance with one embodiment of the present invention. In the block diagram, the power supply for the control system is indicated generally by the unit 161. The pump motor 76' (see'FIGS. 1 and 4) is connected to the power supply, as are the individual paddle motors corresponding to the paddle motor 37 described hereinabove (see FIGS. 3 and 5). The paddle motors following the motor 37 are identified in FIG. 6 by the reference characters 37-2 through 37-7 to correspond to the sand discharge stati'ons122-27 of the scalping tank 111.

The portion of the control system 1% of P16. 6 that is utilized to control operation of the sand discharge station 21 includes a sensing device for determining when sand is being discharged from the station. This sensing device corresponds to the switch 45 (FIG. 3) that determines when the sensing paddle 41 at the initial discharge station is blocked in its rotation. to indicate a sufiicient accumulation of sand to permit discharge from this station. The sensing device 45 is connected in an operating circuit with the power supply 161 and a pair or" timers 111 and 112. The timer 111 is connected through a control unit 113 to the valve actuator 51 for the first valve 61 at the initial discharge station. The timer 112 is similarly connected, through the control unit, to the valve actuator 52. Basically, the timer 111 controls the valve actuator 52. In addition; the two timers 111 and 112 are coupled to the valve actuator 53, by means of the control unit 113, v

for the station 22 includes a sensing' device 45.-'2 thatis connected to a pair of timers 111-2 and 112-2. The. timer 111-2 is connected to a first valve actuator 51-2 at the sand discharge station 22. The timer 112-2 is connected to a second valve actuator 52-21 Both timers 111-2 and 112-2 are coupled to the third valve actuator 53-2 at this discharge station of the scalping tank. Again; all connections are made through the control unit 113. A corresponding arrangement is illustrated for the control of sand discharge station 23, comprising a sensing device 5-3, a pair of timers 111-3 and 112-3, and individual valve actuators 51-3, 52-3 and 53-3. The remaining controls for stations 24-27 are similar. g

When the control system 190 is placed in operation; and after sand has accumulated in the bottom of the tank,- the sensing device 45 senses the accumulation of suii"1 cient sand to permit discharge at station 21. When this. occurs, the timers 111 and 112 are both actuated and these timers complete operating circuits through the fluctuation control units through the valve actuators 51 and 52 respectively. Accordingly, sand is discharged through the valves 61 and 62 controlled by the actuators 51 and 52 as described above, releasing the coarsest. grade of sand through valves 61 and 62 into the associated flumes 65 and 66 The connection from the tirners to the valve actuator 53is such that this valve actuatorrernains unenergized, however, and no sand is discharged through the third valve 63 at the station 21. This action continues, intermittently, depending upon the buildupjof sand,'until such time as one of the timers 111 and 112 times out. Assuming that the timer 111 is the first timer in the system 1911 to completeits operating cycle, the fluctuation control unit 113 maintains the circuit connections the, same as they have been previously for a predetermined delay interval, during which dischargeof sand is continued through both of the vflves 61 and 62, under control of the sensing device 45. At theendof this delay, interval, the operating circuit for the valve actuator 51 is interrupted in the control unit 113., Thereafter, prek suming thatthe timer 112 has not yet counted out, the sand at outlet station 21 is discharged only through the valve 62 controlled by the valve actuator 52. Therealter, when the timer 112 has completed its'cycle of operation and has timed out, the operating circuit for theflvalve actuator 52 is interrupted in the control unit 113 and, the valve actuator 53 is energized so that any subsequent discharge of sand from the station 21 passes through the, third outlet valve 63 at this station and into the third, flume 67 (see FIG. 2). This condition is maintained until the entire control system is reset as described hereinafter. v g p n Operation at the remaining stations 22-27 proceeds in the same manner. Thus, with respect to station 22, the

timer 111-2 maintains the valve actuator 51-2 in operation, whenever the sensing device 45-2 indicates the presence of sufiicient sand to permit a discharge, until the timer has counted out. The timer 112-2 effectsa similar control over operation of the valve actuator 52-2. When both timers have counted out, and both of the valve actuators 51-2 and 52-2 are counted out of operation, the third valve actuator 53-2 is energized to discharge sand 7 to the third or waste flume 67. At the station 23, primary control is effected by the sensing device 45-3. The timer. 111-3 provides direct control of the valve actuator 51-3 and the timer 112-3 controls the valve actuator 52-3. When both timers have timed out, the valve actuator53-3, is energized to divert any further sand discharge from this station to the waste flume through the related valve at the station 23 Operation is the same forthe other sand discharge stations. I

Here in the initial description of the operation of the control system 1011, and particularly of the station .21, reference was made to a time delay following the out of the device 111. This time delay is not'necessarily eifect-ive, however, on each operation of the timer 111. i

operation, the time delay in interruption of the operating circuit for the valve actuator 51-3 is provided by the control unit 113. Thereafter, when the timers 111 and 111-2, and the corresponding timers to the other stations 24-27 complete their operation, no time delay is provided,

Accordingly, when the first one of the timers in the 111 series has timed out, the control unit 113 affords a time delay with respect to de-energization of the related 51 series of valve actuators but upon completion of this delay interval all of the other timers in the series afford instantaneous de-energization of the associated valve actuators when they do time out.

Preferably, a similar time delay is provided by the control unit 113 relative to the second series of valveactuators comprising the devices 52, 52-2, 52-3 etc. That is, when the first timer in the series 112, 112-2, 112-3 et seq. times out, the control unit 113 aifords a predetermined time delay in the de-energization of the associated valve actuator. This delay is provided only with respect to the first timer of the 112 series that completes its operation. After the time timer in this series has completed its operation and the delay interval has passed, the remaining timing devices in the 112 series are effective to cut off the associated valve actuators instantaneously upon completion of their respective timing cycles.

- The timedelay operation atforded by the control unit 113 is highly-advantageous in preparation of specification sands. time delay system, it must be understood that a sand specification ordinarily entails a reasonable range of variation with respectto individual sand sizes. quently, the total discharge from any of the stations 21-27 may be varied to at least some extent without departing from the specification. lfithe input to the scalping tank changes to theextent of affording an increase in the sand particles in the size range that accumulates at station 23, for example, it is frequently quite possible to effect a corresponding increase in the total sand discharged from this station into one or both of the specification fiumes 65 and 66, under control'of the valve actuators 51-3 and 52-3, without departing from the specifications. The time delay afforded by the control unit 113 permits continued operation for a limited interval to enable the control system llfitl to accommodate such a fluctuation in the composition of the input sand to the scalping tank; Of course, the same situation applies at all of the other stations. That is, the time delay control afforded by the unit 113, as described hereinabove, permits continued preparation ofthe two specification sands, initially set up on the two series of timers, without interruption, despite changes in the composition of the input to the scalping tank. This avoids relatively large losses of useful sand which might otherwise occur if rigid control'were exercised by the individual timers;

To understand the advantages afforded by the for the formulation of a relatively large quantity of one specification sand and a substantially smaller quantity of another specification sand. This could be accomplished, in the control system 1%, by adjusting the relative time intervals for the two series of timers 111 and 112, if the resetting of one group oftimers is dependent on timing tional portion of the time in which the other series is effective. In PEG. 6, this is accomplished by means of a proportioning control unit 114 that is connected'to each of the timers in the 112 series. For example, the proportioning control 114 could comprise a simple adjustable-cam motor operated relay for effectively de-energizing or otherwise interrupting operation of each of the timers in this series on a cyclic basis. By reducing the effective duty cycle of the 11 2 series of timers,'the total quantity of sand discharge through the associated outlet valves is reduced, in proportion to the sand discharge through the other. series of valves controlled by the 111 timers. With an arrangement of this kind, the control system 190 provides effective regulation of thequantity of each ofthe two specification sands that are prepared substantially simultaneously by the scalpingtank 10. Of course, the control unit 113 of the system 1110 should also I include reset means for re-initiating preparation of both Consespecification sands after all of the timers in either series have completed their, operation, in order to avoid a continuingdischarge to the waste iiurne 67.

FIG. 7 illustrates a detailed electrical circuit arrangement that may be utilized for the control system 1% described hereinabove in connection with FIG. 6. FIG. 7

includes a complete illustration of a practical operating circuit for the control unit 113 and also showsall ofthe individual paddle motors for the sand-sensing switches. The timing circuit arrangement illustrated in FIG. 7, however, shows only the timers for the first discharge station 21 of the scalping tank, the operating'circuits at the otherstations being substantially identical with this first stations 21-27 are all connected in parallel with each Of course, if'a particular sand specification is limited to small tolerances with respect to individual sizes, then the delay interval permitted by the control unit 113 must be I kept relatively short for that product. hand, where a specification includes relatively broad controlling the'sensitivity of the system 1% with respect to the individual specification sands discharged through the homes and 66 of the scalping tank 113.

In a given installation, it may be desirable to provide Onv the other ranges with respect to individual particle sizes, then the station.

Thus, as illustrated in FIG. 7, the power supply 101 may be a three-phase A.C. supply connected througha three-pole main switch and the power lines 151, 152 and 153 to the motor 76. The primary Winding of a coupling transformer 154 is connected across the power lines 152 and 153.. The terminals 'of the secondary winding of the transformer 154 are connected to a pair of control buses 155 and 155 for the control system. 1

The circuit arrangement ofFlG. 7 includes a starting relay 157 for controlling operation of the hydraulic pump motor 76. The oper'ating'coil 158 of the motor control relay is connected across the buses 1551and156 in'a'circuit that includes, in series, .a switch 159. I In the illustrated arrangement, the relay 157 includes three sets of normally open contacts 161, 162 and 163 interposed in series in the lines 151, 162 and 153, respectively, between the power supply and the motor 76. Y

The individual paddle'motors for the sanddischarge other between. the buses 155 and 156. motor 37 for the first station is shown in conjunction with corresponding motors 37-2 through 37-7 for the other stations. Preferably, a selector switch 165' is interposed in series in the control bus 155 ahead ofv the connection to the paddle motors'but following the connection for the relay 157 that controls the hydraulic pump motor.

The sensing switch 45 is shown in FIG. 7 as a. normally open double-pole switch with one side of each section of the switch connected to the bus 155. Thus, the terminal 1% of a first section of the switch 45 is connected to the bus and the corresponding terminal. 167 inthe second switch section is also connected to the bus. A manually operable timer control switch 168 is connected in parallel In FIG. 7, the

with that section of the switch 45 which comprises the terminal 166.

Each of the timers of the control system, such as the device 111, compirses a motor connected to an indicator by a solenoid ope-rated clutch. De-energization of the clutch solenoid causes the indicator to return to an initial position for the beginning of a new timing cycle. Usually, a spring'bias arrangement is used to reset the timer indicator. The contacts controlled by the timer, described in detail hereinafter, are also actuated by the timer. motor. Timing devices of this kind are commercially available; hence, the details of timer construction are not critical to the present invention. Other forms of timer mechanism may also be adopted without departing in any way from'the present invention.

The timer 111, in the circuit of FIG. 7, comprises an operating motor generally indicated by the coil 171. The timer further includes two sets of normally closed contacts 172 and 173 and two sets of normally open contacts 174 and 175. The first set of normally closed contacts of the timer is connected in a series circuit with the operating coil 51$ for the solenoid-operated valve actuator 51. This complete circuit, between the buses 1'55 and 156, include the first section of the sensing switch 45, the contacts 172, and the solenoid 518. In addition,

the contacts 172 are incorporated in the operating circuit for the-timer motor 171, this circuit comprising the sensingswitch 45, the contacts 172, and the motor 171 in a series. arrangement.

The second-set of normally closed contacts 173 is connected in a series circuit that extends from the bus 155 through the operating coil 177 of a reset relay 1'78 and through a normally closed selector switch 179 to the bus 156. The normally open contacts 174 of the timer 111 are connected in a series circuit that begins at the bus .155 and extends through the contacts 174, through the operating coil 180 of a time delay relay 181, and through the switch 179 to the bus 156.

The reset relay 173 includes onerpair of normally open contacts 182. The contacts 182 are incorporated in series in an operating circuit-for. a seires of individual timer motor clutches 191-197. The clutch solenoid 191 is associated with the-timer 111. The remaining clutches 193through 197 are individually connected ,with the corresponding timers 111-2, 111-3, et seq. in the remaining stages of the control system. That is, the clutch solenoid 192 compirses a part of the timer mechanism 111-2 (FIG.-6), the clutch solenoid 193 is associated with the timer 1-11-3, etc. In each instance, the clutch solenoids are returned to the bus;156.

The control unit 113 further includes a control relay 201 comprising an operating coil 292, a pair of normally opencontacts 203, and a pair of normally closed contacts 2914. Actually, relay apparatus represented by the device 291 would include one set of normally open contacts and one set of normally closed contacts for each such stage. The operating coil 202 of this relay is connected between the two buses 155 and 156 in an operating circuit that includes, in series, a pair of normally open contacts 255 in the time delay relay 181. A bypass circuit is provided with respect to the contacts 205, this circuit including a normally open switch 206 that is ganged with the switch1'79. The normally closed contacts 204 of the control relay .291 are connected in parallel with the normally closed contacts 172 of the timer 111.

The second timer 112 in the control system of FIG. 7 is essentially similar to the timer 111 and includes a .motor represented by a coil'211, two sets of normally closed contacts 212 and 213, and two sets of normally open contacts 214 and 215. The motor 211 of this timer .is connected in a series circuit, beginning at the bus 155,

nected in parallel with the timer motor 211. In this portion of the circuit, a reset relay 218 is included with the operating coil 217 thereof connected through the normally closed timer contacts 213 to the bus 155. The other terminal of the coil 217 is connected through a normally closed switch 219 to the bus 156. The switch 219 is also connected in a circuit that extends from the bus 156 through the switch and through the operating coil 221) of a second time delay relay 221 and thence through the normally open contacts 214 of the timer 112 back to the bus 155. As before, the reset relay 2:18 includes a set of normally open contacts 222. The con- .tacts 222 are incorporated in a circuit for the timer motor clutches 231-237, the clutch solenoids 231-237 all being in parallel with each other. As before, the clutch solenoid 231 is associated with the timer 112 and the remaining clutch solenoids are connected withthe other timers for the second specification sand produced by the scalping tank.

A second control relay 241is incorporated in the fluctuation control unit 113. This relay is similar to the con- .trol relay 201 and includes an operating coil 242, a set of normally open contacts 243 and erect of normally closed contacts 244. Asbefore, the control relay would also include additional sets of normally open and normally closed contacts for each discharge station of the scalping tank. The operating coil 242 is connected between the buses 155and 156 in a circuit that includes, in series, the normally open contacts 245 of the time delay relay 221. In parallel with the contacts 245 there is connected a normally open switch 246 that is ganged with the switch 21?. The normally closed contacts 244 of the control re- .lay 241 are connected in parallel with the normally closed contacts 212 of the timer relay 112.

The operating connection for the third valve control solenoid 535, in the circuit arrangement of FIG. 7, in-

cludes both of the timers 111 and 112 and the control relays 201 and 241. Thus,.this operating circuit, beginning at the bus 155, extends from the first section of the switch 45 through the normally open contacts 175 of the timer 111, the normally open contacts 253 of the relay 201,

through the solenoid 53S, and throughrthe normally open contacts 243 of the relay 241 and the normally open contacts 215 of the timer 112 back to the bus 155. It is thus seen that to energize the third operating solenoid 538,

the one which controls the discharge valve leading tothe waste home, it is necessary to actuate both of the timers 111and 112 and both of the control relays 201 and 241.

In considering operation of a circuit arrangement of FIG. 7, it may first be assumed that the main switch is closed, supplying power to the lines 150-153 and, accordingly, to the control buses and 155. To afford fluid under pressure for the hydraulic valve liftingdevices, the switch 159 is closed to energize the motor starting relay 157. Energization of the relay 157 closes the contacts 161-163 in the line connections to the hydraulic pump motor 76. The motor 76 is maintained in operation continuously during the use of the scalping tank in.

order to have available a supply of fluid, under pressure, at all times. The switch 165 is closed to energize the paddle motors 37 and 37-7, and these motors are also maintained in operation continuously during use of'the scalping tank.

After the foregoing steps have been accomplished, and with the other switches in the position shown, the system is in operation. When sand has accumulated in'the bottom of the scalping tank adjacent the sand discharge station 21 to a height sufiicient to interrupt operation of the paddle rotor 41 (FIG. 5) the sensing switch 45 is closed as described in detail hereinbefore. Closing of the switch 45 energizes the solenoids 51S and 52S, operatingthe valve actuators 51 and 52 to open the discharge valves er and 62 as described above. At the same time, the timer motors 171 and 211 in the timing devices 111 and the sand level has reduced sufficiently to free the rotor 41 for continued rotation, the switch 55 opens, de-energizing the solenoids 51S and 528 to thereby close the sand discharge valves. When this occurs, of course, the timer motors 171 and 211 are also de-energized; it is thus seen that these motors operate only during thetimes in which sand is actually being discharged and, accordingly, afford an accurate measurement or" the quantity of sand flowing into the two specification ilumesoS and 6d.

The foregoing sequence of operations is carried out until one of the timers 111 and 112 completes its timing operation. For purposes of explanation, it may be assumed that the timer 111 completes its cycle of operation before the device 112 times out and before any other timers in the 111 series time out. When this occurs, the contacts 172 and 173 are opened, in the'timer Ill, and the contacts 174 and 175 are closed. Accordingly, the operating circuit for the solenoid SIlS'through the contacts 172 is interrupted. However, the solenoid remains energized through the alternate circuit provided by the normally closed contacts 204 of the control relay 201. This occurs only if the timer 111 is the first in the series of timers that controls the valve for the first-product fiume d5 of the scalping tank, since prior completion of the operating cycle by one of the other timers in this sequence (for example the timers lit-2 or Ell-3, FIG. 6) would prevent continued energization of the solenoid 518 through the alternate circuit.

When the timer 111 has completed its operation, the opening of the contacts 173 is efiective to de-energize the operating coil 177 of the reset relay 178, insofar as the timer 111 is concerned. However, the relay coil 177 is also connected through parallel circuits in all of the other timers in the 111 series .and, accordingly, remains energized. The closing of the contacts 17 on the other contacts 264 of the control relay 2M are opened, thereby opening the alternate energizing circuit for the operating solenoid 518. Thus, after the time delay period for the relay lfil has been completed, both of the parallel energizing circuits for the solenoid 513 are open and, as a consequence, the fir-st outlet valve 61 for the sand discharge station 21 remains closed until reset as described hereinafter.

The control sequence'for the second solenoid528 is the same. Thus, when the timer 112 runs out, the contacts 212 are opened.

which the device 112 is incorporated, the solenoid 5348 remains energized through the circuit comprising the normally closed contact 244 of this control relay. Of course,

it will be understood that energization of the valve control solenoid 528 is always dependent upon the closing of the sensing switch 45. Completion of the tim ng cycle for the device 112 opens the contacts 213, but the reset relay 218 remains energized because other timers in the same series with the device E12 have not yet timed out. Closing of the timer contacts 214, however, energizes the time delay relay 221. As soon as the predetermined delay interval for this relay} has transpired, the contacts 2455 close, thereby energizing the control relay coil As a consequence, the cont-acts 244 of the relay 241 are opened, interrupting the energizing circuit for the second valve solenoid 52S.

if the two control relays 201 and 244; have both been energized, and no reset operation has as yet occurred, as described herinafter, a complete operating circuit is established for the third valve control solenoid 53S. As noted above, this circuit extends through the upper section of g It the control relay 241 has not yet been .tactuated, however, by some other timer in the series in l2. the sensing switch 45, the timer contacts 175, therelay contacts 203 and 243 and the timer cont-acts 215 Thus, until a reset operation occurs, the sand atv the outlet station 21 is discharged through the third control valve 63 operated by the solenoid 53S and this sand goes to the waste ilume 67.

As noted above, the time delay relays 181 and 221 are actuated by the timers 111 and 112 of the first sand discharge-station control apparatus only if these particular timers happen tozbe the first timers in their respective series to complete their timing operation. Of course, one of the other timers in either series may well count out first. For example, a situation may be considered in which the timer 111-2 for the second'sa-nd discharge station 22 completes its timing operation before the timer ill of station 21. When this happens, the'o-perating coil 1% of the relay 131 is first energized through a connection to the timer 11142 corresponding to the connection illustrated for the timer 111 in FIG. 7. Accordingly, when the timer ll completes its operation, the time de lay introduced by the relay 181 is first energized through a connection to the timer 111-2 corresponding to the connection illustnated for the timer 111 in FIG. 7. Accordingl when the'timer lll completes its operation, the

time delay introduced by the relay 181 may have already been completed, and at least has been initiated. Consequently, the time ot-actuation of the control relay 201 is determined :by completion of operation of the timer 111-2 instead of the timer ill. If the time delay relay 181 has already completed its relayoperation before timer H1 counts out, thesolenoid 513 is de-energized immediate'ly upon completion of the timing operation of the device It'll. If the delay interval for the relay 181 has started running but is not completed, the solenoid 518 is de-energized upon completion of the time delay interval started by the counter ll12 instead of requiring a complete time delay cycle from the time that the device 111 completes its operation. The same situation-obtains with respect tothe second time delay, relay 221 in the 312 series of timers and the related control relay 241.

The reset operation for the timers in the 111 series is control'le d by therelay 1'78. As indicated in FIG. 7, the openating coil 177 of this relay is connected to all of the timers in the 11 1 series, afiording seven separate parallel energizing circuits to the bus E55. When the last of the timers in the 11.11; series counts out, all of the clutch solenoids @1497 erode-energized by theopening of the contacts 132. When this happens, the indicators of the timers timers, the 112 series, is the same, the second reset relay .213 having its operating coil 217 connected in seven independent energizing circuit through the individual timers of this series. It is thus seen that resetting of the timing control apparatus for each of the two specification sands I produced simultaneously under control of the system 1% is independent of the other; where there is any substantial difference between the two sand specifications, this independent resetting of the two series of timers is of substantial advantage in preventing excessive dumping of sand through the waste fiume while awaiting the completion of one or two timing operations with respect to only one of the different specification sands.

'In some instances, it may be desirable to control opera tion of thesystem independently of the'sensing switch t5.

' With respect to, the. ill timer, this can beaccomplished by means of the vm-auallyactuated timer control switch 168,. which is connected in parallel with the first section of the 'sensing switch Of course, a similar manual 13 control switch may be incorporated in the system in parallel withthe second section of-the sensing'switch 45in control completely. For this purpose, the switches" 179 and 206 may be actuated simultaneously, opening" the switch 1 19'and closing the switch 295 When this is done,"

the opening'of the switch 179' prevents actuationof the timedelayrelay 181 and the'closing of the switch 206 provides a directenergizing connection" for the control relay 201 to the bus 155; The motor of the timer 111f isnow energized, up on closin'g of the sensing switch 45" or the rnanual'switch 168. But the timer clutch solenoid 191'is heldde-energized'by the open circuit in the" contacts 182 of the reset relay 178i Hence, the timer cannot carry; out a' timingoperation, because of'the open circuit for thereset relay 17 8 m; the switch 179. Consequently, the solenoid 53S controlling discharge to the waste flame cannot be energized un less the timers in the 111 series are set manually to'zeroi V The ganged switches 219 and 246 afford the" same" operating results'with respect to the time delay relay 221, the' res'etrelay zlli, the com-011mm 241 that are connectedto the second timer 112'. Thus, if the switches 219 a'nd246are also a btuated' to their" alternate operating positions, in the same manner as described above with respect to the. switches 17 s and 206, the timer 112 cannot countout. However, if all of the switches'1'79, 2G6, 219 andj246' are actuated to their alternate'positions and the timers 111 and 112 are set manually to zero, then all sand' is thereafter discharged to the waste time under control of the solen oid 538. Of course, the entire automatic control system can be tie-energized by opening of the switch 165, which cuts off that portion of themain bus 155 that energizes the'elec trical system.

In the description of FIG. 6, reference was'rnade to a proportion control device 114. To incorporate this device in the circuit of FIG. 7, it is only necessary to return the lower section of the switch 45 to the bus 155through the proportioning-control device. That is, the device 114 would be interposed in series between terminal 167 and the bus 155: to permit effective variation of the duty cycle for the portion of the control circuit actuated by the timer 112 as compared with that actuated by the timer 111.

FLG. 8 is a simplified block diagram of a control system for the scalping ta'nli 10, constructed in accordance with another embodiment of the present invention. In this diagram, the power supply, the pump motor, and the paddle motors have not been illustrated, since the arrangement is the same, in this respect, as in the embodiment of FIGS. 6 and 7.

The portion of the control system 360 of PEG. 8 employed to control operation of the sand discharge station 221 campuses the sensing device 45 that is utilized to sense the discharge of sand from this station of the scalping tank. Thus, sensing device 45 corresponds to the switch 45 shown in FIG. 3. Sensing device 45 is connected to a first-product minimum timer 311 and to a first product maximum timer 312. Maximum timer 312. is provided with two output circuits. One of these output circuits is used to connect the sensing device 45 to a second-product minimum timer 313 and to a second-product maximum timer 314. e

The second output circuit of the first-product maximum timer 312is connected to the valve actuator 51 that controls discharge of sand through the first product valve in the initial discharge station 21 of the scalping tank. This is not the only control for valve actuator 51; the valve actuator is also controlled by a circuit connection from the minimum timer'gll through a first product minimum contiol circuit 3l 5 that is connected to all stages of the control system 368.

The second-product maximum timer 314 is provided with one output circuit connected tothe valveactuator. 52 forthe second discharge valve 62. Actuator 52, as before, controls the dischargeto'the second specification" product. This same timer 3l4 also hasa second output" circuit connected to the valve actuator 53 that actuates the waste-discharge valve 63 'of-the' scalping tankz The remaining timin'gidevice' of thefirst stage, thesecondproduct minimum timer 313, is connected to valve actuator 52- 'through a "second product minimum 7 control circuit 316. Thus, valve'actuator 52- is controlled in its operation-byboth of the timers -313'and 314 -asexplained in detail hereinafter.

Thebasic control'circuit for the second discharge station 22, in the systemlitltlfof FIG. 8; is essentially-thesame as that for station 21; 45-2 is electrically connected to afirsuproduct minimum timer 311-2 and tea first-product maximumtimer- 312-2. The first-product maximum timer 312-2 has two output circuits. As'in thefirst described station of the system see; the secQnd product maximum timer 312-2 has-one= output circuit connected to the first specification discharge valve actuator 51-21 This same valve actuator-is also controlled by the first-product minimumcontrol circuit 315, the circuit 315 being provided with an input connection from the minimum-"timingcdrcuit 311-2. The-remaining output circuit of timer 312-2 is-connected to -asecond-productminimum timer 313-2- and to a secondproduct maximum timer 314-2.

Thesecond maximum timerSM-Z has one output connected to the second specification product valve actuator 52-2- and a second output connected to the waste product valve actuator" 53-2. The valveactuator 52-2 controlling the discharge to the second product flume, at the second discharge station, is also connected to the second-product minimum control circuit 316, which is providedwith a further input from the timing, circuit 313-2. 1 v

The circuits are duplicated at each of the remaining stations 23-27 which, accordingly, have been omitted from FIG. 8. It should be noted thatthere is only one minimum control circuit 315, for the first' product to be discharged, connected to all stations. The circuit 315 is provided with an input connected to each of the firstproduct minimum timers 311, 311-2, et seq. Similarly,

there is only one minimum control circuit for the second.

product, circuit 316; which utilizes input signalsfrom each of the second product minimum timers 313, 313-2 et seq.

The preferred control system 309 of FIG. 8 also includes a product ratio control unit 318 that is connected to all stages of the system. Unit 318 has an operating circuit connecting sensing device 45' to each of the secondproduct timers 313 and 314 of the first stage of the control system. A similar operating circuit in the ratio control 318 connects sensing device 45-2 to' the secondpr'oduct timers 313-2 and 314-2. Corresponding operating circuits are provided for the remaining stages of the control system. Each such operating circuit includes at least one set of control contacts, exemplified by contacts 319 and 31-2.

The ratio control unit 318 may constitute any desired apparatus capable of opening and closing the control contacts 319 and 319-2. Preferably, the open-to-closed duty cycle or ratio of the device should be adjustable to provide a means for adjusting the quantity of the second specification product relative to the first product. Suitable adjustable percentage timers are readily available on a commercial basis.

In setting up the control system 300 of FIG. 8 for two given specification products, timer 311 is set for a minimum quantity of material required to be discharged fromthe initial discharge station 21 of the scalping tank. Timer 312, on the other hand, is set for a maximumquantity of this same material in the first specification product. It is thus seen that the timer 311 performs the same basic Thus, the second sensing device- 15' function as the timer 111 in the System 1% (FIGS. 6 and 7). Timer 312, on the other hand, functions in a manner quite similar to the time delay circuits used in the first-described control system in that it establishes a maximum discharge that may be permitted once the minimum amount of material from the first discharge station has been supplied to the first specification product. v a

The second-product minimum timer 313 is set for the required minimum discharge of material from station 21 to the second specification product. Again, the maximum timer 314 affords a limit on excess discharge of the material from station 21 into the second product, defining a tolerance range for material from this station in the second specification product. Corresponding settings are required for the individual timers at stations 22 through 27, each station being set for both minimum and maximum levels to be discharged into both'the first and second product flumes. I

Usually, one product predominates, in the'output of the scalping tank, from the standpoint of required quantity. On the other hand, a certain minimum quantity of the second specification product is often essential. The ratio control unit 318 is set to actuate the second-product timer and actuation circuits a given percentage of the time, in the approximate ratio of desired quantity of the second product relative to the first.

When the system is placed in operation, and after a. quantity of sand is accumulated in the bottom of the scalping tank, the sensing device 45 registers the accumulation of sufficient sand to permit a discharge at station 21. When this occurs, the two first-product timers 311 and 312 are energized and an operating circuit is established, through timer 312, energizing the valveactuator 51 to open the first-product discharge valve 61. Accordingly, sand is discharged through the valve 61 and into the first product flume 65. Assuming that contacts 319 are open, neither of the valve actuators 52 or 53 is energized, and there is no discharge either to the second specification product or to the waste flume. Thisaction continues on an intermittent basis, depending upon the build-up of sand at station 21,'unti1 the minimum timer 311 times out.

As operation continues, contacts 319 are closed, in ratio control unit 318, on a cyclic basis and in accordance with the duty cycle for which the control unit is set;

Whenever contacts 319 close, timers 313 and 314 are energized and an operating circuit is established from completed its timing operation, .the operating circuit for valve actuator 52 is opened to prevent further discharge ofm'aterial from station 21 to the second-product specification flume. Timer 314, at this time, switches its output from actuator'52 to valve actuator'53, thus discharg- 1 ing any further accumulation of sand at station 21 into the waste flume.

From the foregoing description, it will be seen that the maximum timers 312 and-314 afford the basic control for the valve actuators at. each station. The minimum timers 311 and 313, and the other minimum timers in their respective series, however, have a definite and equally important function. Thus, when all of the minimum timers for the first-product timing devices 311, 311-2, et seq., have timed out, then the first product minimum control circuit 315 operates to effectively disable each of the valve actuators 51, 51-2, etc. momentarily and to re-set all of the first-product timers for another run. Stated differently, when the last of the minimum timers for the firstspecification product completes its timing operation, there is no substantial delay in starting the next first-prod- ,uct run' at all stations, even though some or all of the maximum timers are not timed out. The same sort of control is afforded by the second-product minimum control 316. That is, when the last of the maximum timers 313, 3132 et seq. times out, the system operates virtually instantaneously to re-set the timing controls for all of the valve actuators in the 52 series and prevent further discharge to thewasteflume.

timer 31 to the second-product Valve actuator 52 to open the second-product discharge valve 62. Hence, during a part of the time only the first product receives material from station 21; at other times material is discharged to both products, the time ratio being controlled by unit 318. The rate of discharge to the first product is not reduced when there is a discharge'to the second product, since valves 61 and 62 are in parallel with each other. ever, the increase in total flow caused by opening valve 62 does reduce the sand level faster, cutting off the flow when sensing device shows insufficient sand available.

Assuming that minimum timer 311 is the first timer in the control system 3% to complete its operating cycle, the associated maximum timer 312 maintains the firstproduct valve actuator 51 at this' station in operation even though the minimum timer 311 has timed out. But when Howthe first-product maximum timer 312 completes its opcrating cycle, it operates to interrupt the energizing circuit to valve actuator 51. That is, upon timing out the timer 312 switches from the output circuit connected -to actuator 51 over to the .output circuit'connected to the second-product timers 313 and 314.

When the second-product minimum timer 313 has timed out, and again assuming that other minimum timing devices in the same series have not completed their station 21. Thereafter, however, when timer 314 has In the foregoing description, it is assumed that separate settable timers are used for each of the timing devices 311, 312, 313, 314, et seq., and this is usually the simplest construction. But timers 311 and312 may be combined in a single timing device providing for both maximum and minimum' settings, since both timers are concerned with measurement of the discharge controlled by actuator 51.

FIGJ9 shows, in schematic detail, a specific control circuitthat may be utilized for one of the stations, such as station 21, 'of' the control system .3411 As shown therein, the first-product minimum timer 311comprises a motor or other operating element 321 and two sets of normally closed contacts .322 and 323. The minimum timer 312 is of similar construction and includes an operating coil or motor 331, two sets of normally closed contacts 332 and 333, and a pair of normally open contacts 334. Thesecond-product maximum timer 314 is of the same construction, having an operating coil or motor 341, normally closed contacts 342 and 343 and normally open contacts 344. The fourth timer, the second-product minimum timer 313, is again like timer 311 and -is. provided with a motor 351 and two sets of normally closed contacts 352 and 353.

In FIG. 9, the paddle motors, motor relay, and similar power circuits are not illustrated, since these may be the same as shown in FIG. 7. Thus, the only portion of the power circuits illustrated in FIG. 9 is the busses and 156, corresponding to the-similarly numbered elements in FIG. 7. Y

. As described hereinabove in connection with FIG. 8, the main control element for the circuit shown in FIG. 9 is the sensing switch 45. One terminal of this switch is connected to the bus 155 and the other terminal of the switch is connected through the normally closed contacts 333 of the first-product maximum timer 312 to the operating solenoid 518 of the first product valve actuator, the solenoid being returned to the bus 156. The sensing switch is also connected through contacts 333 and through the normally closed contacts 332 of timer 312 to the motor 3310f the timer, the motor being returned to bus 156. A third branch of this same circuit extends through contacts 333 and through the normally closed contactsf323 of the first-product minimum timer 311 to the operating motor 3.21 of the timer, the latter being returned to bus 156.

As in the previously-described embodiment, the individual timers used in the control system 3% may be provided with electrically actuated clutches which are maintained energized at all times during operation of the timers and which, when de-energized, permit resetting of the timers by suitable spring or other return means. In FIG. 9, the operating coils for the clutches of all the first product timers are grouped at the right-hand side of the drawing, being shown as coils 311-C through 312-7C. One terminal of each of these timer coils is connected to bus 155. The coils are all connected in parallel to a pair of normally open contacts 354 in a reset relay 355, the other side of contacts 354 being connected to bus 155. Re-set' relay 355 is provided with an operating coil 356 having one terminal connected to bus 156 and the other terminal connected through the normally-closed contacts 322 of the minimum timer 311 to the bus 155. Only the one re-set relay 355 is required for all of the first-product timers of the entire control system 36%); the operating coil 356 of the relay is connected to the conductor 155 through a pair of normally-closed contacts in each of the first-product minimum timers. V

In the form shown in FIG. 9, the ratio control unit 313 comprises a ratio timer 371 and a ratio control relay 372; The timer 3'71 comprises a motor 373 that alternately opens and closes a pair of contacts 374 in accordance with the duty cycle for which the timer is adjusted. The control relay 372 comprises an operating coil 375, the normally open contacts 319, and a pair of normally closed contacts 37?. Control relay 372 would also include a set of normally open contacts and a set of normally closed contacts for each of the remaining stages of the system. To save space in the drawing, only one additional group of contacts, comprising the normally open contacts 319-2 and the normally closed contacts 379 is shovm.

The motor 373 of the ratio timer 371 is connected through a manually operable switch 381 to the bus 155. The other tenrninal of the relay coil is also returned to the bus 156. It is thus seen that the control relay 371 is alternately energized and de-energized upon closing and opening of the timer contacts 374 in accordance with the duty cycle for which the timer 371 has been set.

The sensing switch 45, in addition to the circuit connections set forth above, is also connected in a circuit that includes, in series, the normally open contacts 334 of tirner'312, the normally closed contacts 3'77 of ratio control relay 372, the operating solenoid 53$ for the second product valve actuator, the normally closed contacts 343 of the second-product maximum timer 314,

' and the bus 156. A branch of this same circuit extends from the contacts 334 through the normally closed contacts 342 of timer 314 to the operating motor 341 or" the timer and back to the bus 156. In the specific circuit shown in FIG. 9, the relay contacts 377 are incorporated in series in this circuit, as compared with the simpler direct connection of FIG. 8. Another branch or" the same circuit extendsthrou'gh the normally closed contacts 353 of the second-product minimum timer 313' to the operating motor 351 of this timer, which is also returned to the conductor 155. 1

There isan alternate circuit connecting the sensing switch 45 to the second-product actuator solenoid 528. This circuit extends from switch 45 to the normally-open contacts 319 of the ratio control relay 372, and then to the solenoid, the circuit being completed through contacts 343 of timer 314. The same circuit affords a connection to timer motors 341 and 351, through the timer contacts 342 and 353, respectively.

The operating circuit for the waste-product valve actuator solenoid 538 extends from the sensing switch 45 through the normally open contacts 33 of the firstproduct maximum timer 312 to the solenoid, and from 4 timers for operation.

. 18 t the solenoid through the normally open contacts 344 of the second-product maximum timer 341 back to bus 156.

The operating coils for the clutches for all of the second product timers are shown as the group of coils 313-0 through 314-7C at the right-hand side of the drawing. These clutch solenoids are all connected in parallel with each other from the bus 156 to a pair of normally open contacts 362 in a re-set relay 351. The other side of contact pair 352 is returned to the bus 155. One terminal of the operating coil 363 of re-set relay 36 1 is connected to conductor and the other terminal of the operating coil is returned to bus 155 through the normally closed Contacts 352 of the second product minimum timer 313, Additional parallel connections tob-us 155 are provided through a corresponding series of norm-ally closed con? tacts in each of the second-product minimum timers of the control system 366.

In considering the operation of the circuit arrangement of FIG. 9, it may first be assumed that all of the minimum and maximum timers of the circuit have been reset, so that the contact conditions are all as illustrated in the drawing. Under these circumstances, the control relay 355 is energized, through the operating connection to its coil 355 provided by the normally closed contacts 322 of the first-product minimum timer 311. As a consequence, relay contacts 354 are closed and all of the timer clutches 311-6 through 3124C are energized, conditioning the Similarly, the reset relay 361 is energized through the connection afforded by the normally closed contacts 352 of the second-product minimum timer 313. Thus, the relay contacts 362 are closed and each of the timer clutches 313C through 314-7C is energized. Accordingly, all of the maximum and minimum timers are conditioned for operation with respect to the second product as well as with respect to the first product.

When suflicient sand has accumulated at station 21 of the scalping tank, the sensing switch 45 closes. This completes an operating circuit for the valve actuator solenoid 513, the circuit extending from switch 45 through the normally closed contacts 333 of timer 312 to the solenoid. Through this same circuit, the minimum timer 311 for the first product is energized, this connection extending through the timer contacts 323. Moreover, the maximum timer 312 for the first product is energized through its own normally closed contacts 332. On the other hand, there is no energizing circuit completed to either of the solenoids 523 or 538, nor is there an effective operating circuit established for either of the secondproduct timers 313 and 31 5, assuming for the moment that theratio timer 371maintains its contacts 374 open and that, accordingly, the ratio control relay contacts 376 p are open. The effect of the ratio control unit 318 will be described after the other operating circuits have been considered.

When sensing switch 45 has been closed for a cumulative total time corresponding to the setting of the firstproduct minimum timer 311, the timer times but, opening both contacts 322 and 323. The opening of contacts valve 61 to the first-product flume each time the solenoid 518 is energized by the closing of switch 45.

At a subsequent time, and depending. upon the setting of the first-product maximum timer 312, the timer 312 times out. When this occurs, contacts 332 and 333 are opened and contacts 334 are closed. The opening of contacts 332 breaks the energizing circuit to the operating The closing contacts 334 establishes a circuit.

tacts and through the normally closed contacts 377 of the ratio control relay 372 to thesecond-product actuator solenoid 525. This circuit, which is completed through the normally closed contacts 343 of the second-product maximum timer 314, energizes the solenoid and causes it to open the second-product discharge valve to 'dich'arge sand from'station 21 to the second-product flame. The

same circuit is effective to energize the maximum timer 2g out, openingof its contacts 352 breaks the energizing circuit for the coil 363 of control relay .361. This causes the contacts 362 to open and de-energizes all of the second-product clutch coils 313-C through 314-7'C. Again,

control relay 361 is preferably constructed to afford a short delay in re-energizationto provide a sufiicienttime shown-in FIG, 9 is thatsome components for the second 314, through its own contacts 342, and to energize the minimum timer 313 through its contacts 353. During subsequent operation, therefore, the sand is diverted to the second-product flume.

As operation continues witlrthe sand from station 21 being discharged to the second-product fiume, thecumulative time of discharge eventually matches the setting of minimum timer 313. When this occurs, timer contacts 352 and 353 are opened. The opening ofcontacts 353 de-energizes the second-product minimum timer. The opening of contacts 352 breaks one of the energizing circuit for re-set relay 3611. Assuming that timer M3 is the first, or one of the earlier second-product minimum timers to time out, however, control relay ?i6 l'r'emains ener-J gize d through the parallel circuits connected to the secproduct mayfnot be made available to that product. Thus, if the. input sand is of very limited content. with respect to a given constituent size, all of that particular size sand -may be consistently discharged to the first product andmay never accumulate'to an extent sufiicient to provide for discharge of any of that particular constituent to the second specification product This result is'effectively avoided by the-ratio control 318 comprising the ratio timer. 371 and the control relay 372.

Thus,'and as noted hereinabove, during the given time interval comprising the'comple'te operating cycle for the ratio timer 371, the contacts 374, are closed for a predetermined period. Each time the contacts 374 are closed, the operating coil 375 of the control relay 3'72 ond-product minimum timers in the other stages of the system. Consequently, there is' no change in the prod-' uct diversionand the sand continues to be discharged to the second-product ilume. I

Thereafter, the cumulative time during which switch is closed may reach the setting of the second-product maximum timer 314. When this occurs, contacts 542 and 3-4 3 are opened, and contacts 344 are closed. The

opening of contacts 342 de cnergizes timer 314 and con-j ditions it for resetting. The opening of contacts breaks the operating circuit for the second-productiactuator solenoid 52S and prevents subsequent opening of the second-product discharge valve. The closing of con-' tacts 34 i completes an operating circuit for the Waste discharge actuator solenoid 53S. Consequently, continu ing operation of the system results in the encrgization of solenoid 535 each time the switch 45 is closed so that all of the sand accumulated at station 21 is thereafter discharged to the waste ilume. I

The foregoing description is based upon the assumption that minimum timer fil'ltimes out prior to atleast one is energized closing contacts 319 and opening contacts 377. Closingof sensing switch 45, at a time when control relay 372 is actuated, completes an operating circuit to the solenoid 528 through the contacts 3.19. .As a consequence, a part of the sandat-station 21 is discharged to the secondproduct flurne, even though the first-product timers have not yet timed out. Ofcourst, it is necessary to account for the discharge of the sand to the second product and 'thisis accomplished by the illustrated circuit because the minimum and maximum timers 313 and 314 are energized each time the valve actuatorsolenoid 528 is energized.

It is thus seen that the ratio control unit 318 performs It assures-at least a minimal discharge of all of the diiferent component sands required for the econd specification product, since it controls all stages of the control system in a cyclic manner. time, it affords a convenient means for adjusting the relative quantities of the first and second specification prod-' ucts because the duty cycle for the ratio control can be A adjusted to provide a greater or lesser ratio of second of the other first-product minimum timers. On the other A hand, if timer 311 is the last of the first-product minimum timers to complete its set cycle, then the opening of contacts 322 serves to interrupt the last remaining circuit connection for the reset relay 35%. Under these circumstances, the re-set relay is tie-energized and its contacts 354- are opened. When this occurs, the timer clutches for all of thefirst-product minimum and maximum timers, represented by the clutch coils fill-C through 312-7C, are de-energized. These timers are now all re-set, as by a spring mechanism or other suitable means, restoring the timers to their original operating conditions. Preferably, the relay 355 .afiords a quite limited time delay before it can be again energized, the time delay being only sufiicient As a conse- V to allow the timers to re-set themselves. quence, the entire circuit of FIG. 9 is restored to its original operating condition, with respect to the first prodnot, and production of the first specification product is resumed. a

Essentially the same action is eiiected by the re-set relay 3451 upon timing out of the last of the minimum timers represented in FIG; 9 by the minimum timer 313 for the first stage of the system. Thus, if timer 313 is the last of the second-product timers to time ing claims.

product relative to the first. It Will be appreciated that the constituent tolerances for the second product may be either greater or less than for the first product, depending upon the settings of the timers.

The system Btltl of FIGS; 8 and 9 can be easily adapted, like thefirst-described system, to afiord asimple sinle specificationproduct control. To this end, the secend-product timers 313, 314 and the associated secondproduct minimum control 316 areeliminated. The ratio control circuits' may be omitted, particularly Where there is to be no second specification product. It is thus seen thatthe second embodiment of the invention retains all of the flexibility and versatilitylofthe first.

Hence, Whilejpreferred embodiments of the invention have been described and illustrated, it is to be understood that they are capable of variation and modification, and

1 therefore ,do not wish to be limited to the precise de-' tails set forth, but desire to avail myself of such changes and alterations as fall within-the purview of the follow- I claim: a

1. A: control system'for a Water scalping tank or like classifying apparatus for granular material having a series of outlet stations each including first, second and third outlets, saidcontrol system comprising: a first, a second,

f and athird series of outlet operating means, oneof each for each outlet station, for opening and closing said first,

At the same tuatable from a first operating condition to a second operating condition, upon discharge of a predetermined amount of material through the associated one of said first outlets, actuation of each timing means being effective to close the corresponding outlet at each station and divert subsequent discharge to the other outlets at the same station; and means, connected to the third series of outlet operating means, for preventing discharge through any of said third outlets except when both the first and second outlets at the same station have been closed by the associated timing means.

2. A control system for a Water scalping tank or like classifying apparatus for granular material having a series of outlet stations each including first and second specification outlets connected to first and second specification flumes, md each further including a third outlet connected to a Waste fiurne, said control system comprising: a first,'a second, and a third series of outlet closure means, one of each for each outlet station, and each comprising a solenoid-operated valve, for opening andclosing said first, second, and third outlets, respectively; a first and a second corresponding series of individual timing means each including a motor-operated settable relay individually connected to the outlet closure means at one of the respective outlet stations, for measuring the discharge time of material through respective ones of said first and second outlets, respectively, each of said timing means being actuatable from a first operating condition to a second operating condition, upon discharge of a predetermined amount of material through the associated one of said outlets, to thereby close said one outlet closure and divert subsequent discharge to the other outlets at the same station; means for actuating the third outlet closure means for each station to maintain the third outlet closure closed at all timse except When both timing means for that station have timed out to minimize discharge to outlets, each having an associated outlet closure, said con trol system comprising: a first and a second series of individually settable timing means, one of each series for each station, for measuring the discharge time of material through respective ones of said first and second outlets, respectively, each of said timing means being actuatable, on timing out, from a first operating condition to a second operating condition upon discharge. of a: predetermined amount of material through the associated one of said outlets; a corresponding series of first outlet closure operating means,.each connected to a respective one of said first series of timing means, and each operable to control the associated first outlet closure to prevent discharge through the first outlet of a respective one of said stations upon actuation of the associated timing means to its second operating condition; a corresponding series of second outlet closure means, connected to respective ones of said second series of timing means to control the as sociated second outlet closure to prevent discharge through the second outlet of each station upon timing out of the associated timing means; a corresponding series of third outlet closure operating means, individual connected to both timing means at the respective stations, for-con trolling the associated third outlet closure 0 prevent disoutletclosure operating means of said first and second,

series, respectively, for a preselected delay interval follow ing actuation of the firstof said timing means in the series to time out to its second operating condition, and for maintaining preventive operation of the third outlet closure operating means at each station until expiration of the delay interval for both series of timing means.

said Waste fiume; and sensing means, connected to each of said timing means and outlet closure means, for inhibiting operation of the timing means and for actuating the outlet closure means to maintain all outlets closed except when a predetermined amount of material is available at each outlet station. V

3. A control system for a Water scalping tank or like classifying apparatus for granular material having a series of outlet stations each including first, second and third outlets, said control system comprising: a first, a second, and a third series of outlet closure means, one of each through the associated one of said first outlets, actuation of each measuring means being efiective to close the corresponding outlet closure at each station and divert subsequent discharge to the other outlets at the same station; and means, connected to the third series of outlet closure means, for preventing discharge through any of said third outlets except when both of the closures for the first and second outlets at the same station have been closed by the associated measuring means.

4. A control system for a water scalping tank or like classifying apparatus for granular material having a series of outlet stations each including first, second and third 5., A control system for a Water scalping tank, or'like classifying apparatus for granular material having a series of outlet stations at which different classes of material accumulate at varying rates, each outlet station including a first outlet and an auxiliary outlet, each outlet having a closure, said control system comprising: a first and an auxiliary series of outlet closure operating means, one of each for each outlet station, for opening and closing said first and auxiliary outlet closures, respectively; means connected to said outlet closure operating means for inhibiting opening of both outlet closures at each station until sufficient material accumulates to permit discharge thereof at a relatively constant rate; a corresponding series of measuring means individually connected to the outlet closure operating means at the respective outlet stations,

for measuring the discharge of material through respec- V tive ones of said first outlets, each of said measuring means being actuatable fro rna first operating condition, to a second operating condition in response to discharge of a preset amount of material through said corresponding first outlet, each of said measuring means effectively controlling its associated first and auxiliary outlet closure operating means to discharge material through the corresponding first outlet when the measuring means is in its first operating condition, and to close the first outlet closure and divert subsequent discharge through the related second outlet; and delay means, coupled to all of said measuring means, for deferring the diversion of discharge to said second outlets for a preselected interval following actuation of the first-of said measuring means to its second operating condition.

6. A control system for a water scalping tank or like classifying apparatus for granular material having a series of outlet stations each including first, second and third outlets, each having an associated outlet closure, said control system comprising: a first, a second, and a third series of outlet closure operating. means, one of each for, each j series of timing means individually connected to the first determined amount of material through'the associated one of said outlets, to thereby close said one outlet and divert subsequent discharge to the other outlets at the same station; meansrfor actuating the third outlet closure being actuatable from 'a first operating condition to a second operating condition, upon discharge of a predetermined amount of material through the associated one of said first outlets, actuation of each timing means being effective to actuate the associated closure operating means to close the corresponding outlet closure at each station and divert subsequent discharge to the other outlets at the same station; means, connected to the third series of outlet closure operating means, for preventing discharge through any of said third outlets except when the closures for both the first and second outlets at the same station have been closed by the associated timing means, for deferring the closing of the closures for. the

first andisecond outlets, under control of the timing means:- 7 in each series, for a preselected interval followingactuw tion of therfirst of said timing means to time out in each series. a

7. A control system for a water scalping, tank or like classifying apparatus for granular material having a series of outlet stations at which different classes of material accumulate at varying rates, each outlet station including at least a first o utletand an auxiliary outlet, each outlet having an outlet closure, said control system comprising: a first, and a second series of outlet closure operating means, one of each foreach outlet station, actuatahle between open and closed control conditionsfor opening and closing said first and auxiliary outlets, respectively;

means connected to said outlet closure operating means for inhibiting opening of both outlet closures at each] connected to the. outlet closure operating means at :the

respective outlet stations, for Imeasuring the discharge time of material through respective ones of said first outlets, each of said timing means being actuatable from a first operating condition, in which the associated. first out let closure operating means is actuated to its open condition and the related second outlet closure operating means is closed, to a second operating condition, in which the operating conditions of the outlet clos'ure operating of all timing means in the series.-

means for each'station to maintain the third outlet closed at all times except when both timing meansfor that station have timed out to minimize discharge to said Waste fiume; sensing means, connected to'each of said timing means and outlet closure means,'for inhibiting, operation of the timing means and for actuating the'outlet closure means to maintain all outlets closed except when a pre-' determined amount of material isavailable at each outlet station; delay means, coupled to all of said timing means, for deferring the diversion of discharge from said respect to eachserie'sof outlets, following actuation of the first of said timing meansto time out in the series of timmeans; and delay means, coupled to all of said timing ing means associatedwith said ,seriesof outlets; and automatic reset means for re-setting' each series of timing means, independently of the other series, upon timing out 9. A control system for awater scalping tank, or like classifying apparatus for granular material, having a'series o of outletrstations each including at least a first outlet and 'an auxiliaryoutlet, each outlet havingan outlet closure,

said control system comprising: a series of individual independentlysettable timing means, one for each station, 'for establishing maximum and minimum discharge times and for measuring the discharge times of-material through respective ones'ot saiclfirst outlets; ;a corresponding series of outlet closure operating means, each connected to a respective one of said timing means, and operable to close the first outlet closure at each station and divert subsequent discharge through the auxiliary outlet thereof upon timing out of the associated timing means at its maximum discharge time; and means for resetting all of said timing means upon timing out of all of said series at their respective minimum discharge times to re-initate discharge through said first outlets. I p e r 10. A control system fora waterscalping tank, or like classifying apparatus for granular material, having a series of outlet stations each including at least a first outlet and'an auxiliary outlet, each outlet having an outlet I closure, said control system comprising: a series of indimeans are reversed, upon discharge ofa predetermined amount of material through the associated one of said first outlets, to thereby divert subsequent discharge through vidual independently settable; maximum timing means, one for each station, for measuring the discharge time of material through respective ones of said first outlets; a similar series of individual independently settable minimum'timing'means, one for each station; acorresponding the auxiliary outlet of the station; delay means, coupled to all of said timing means, for deferring the diversion of discharge to said auxiliary outlets for apreselected inter-' val followingactuation' of the vfirst of said timing'means to time out; and automatic reset means for resetting all of said timing means to said first operating condition when all have timed out. a V Y a series of; outlet closure operating means, each connected to a'respective one of said maximum timing means, and

operabletofclose the first outletjclosure. at each station I and divert subsequent discharge through the auxiliary out- 8. A control system for a water scalpin'g tankor like classifying apparatus for granular material having a'series of outlet stations each'includin'g first and second s'pecification outlets connected to first and second specification' fiumes, and each further including a third outletconnected toa waste fiunie, said control system comprising: a first, a second, and a third series of outlet closure means, one of each for each outlet station, and each comprising a solesaid first, secondfand thirdfoutlets, respectively; a first and a-second corresponding. series of individual timing means each including a motor-operated settable relay individually connected to thefoutlet closure means at one d5 rnoid-operated valve, for effectively opening and closing of the respective outletstations, for measuring the dis- I charge time of material through respective ones of said first and second outlets, respectively, each-0f said timing 'let thereof upon timing out of the associated maximum timing means; a corresponding series of 'sensing means,

.the sensing means at each station connected to said maximum and minimum timing means for said station, for limiting operation of said timing means and outlet closure operating means to periods in which a sufiicient supply of material'is available to permitldischarge at a relatively constant rate; and means for resetting all of said timing means upon timing out of all of said minimum series timing means to re-initiate discharge through said first outlets. L o

11. A control system for a water scalping tank, or like classifying apparatus for granular mate'nial, having a series'of outleti'stations each including a first outlet, a second outlet, and an auxiliary outlet, each outlet having an outlet closure, said control system comprising: a first and a second'seriesof individual-independently settable maximum timing means, one'for each of said first'and I secondroutlets at each station, for measuring the dismeans being actuatable froma first operating condition to a second-operating condition, upon discharge of a precharge time of material through respective ones of said first and second cutlets; a first and a second similar se means, one for each of said first and second outlets at each station; a first series of outlet closure operating means, each connected to a respective one of said first series of maximum timing means, and operable to close the first outlet closure at each station and divert subsequent discharge through the second outlet thereof upon timing out of the associated first maximum timing means; a second series of outlet closure operating means, each connected to a respective one of said second series of maximum timing means, and operable to close the second outlet at each station and divert subsequent discharge through the auxiliary outlet thereof upon timing out of the associated second maximum timing means; means for resetting all of said timing means of said first maximum and first minimum series upon timing out of all of said first minimum series timing means, and means for resetting all of said second maximum and second minimum series upon timing out of all of said second minimum series timing means.

12. A control system for a Water scalping tank, or like classifying apparatus for granular material, having a series of outlet stations each including a first outlet, a

second outlet, and an auxiliary outlet, each outlet having an outlet closure, said control system comprising: a first and a second series of individual independently settable timing means, one of each series for each station, for establishing maximum and minimum discharge times for respective ones of said first and second outlets; a first series of outlet closure operating means, each connected to a respective one of said first series of timing means, and each operable to close the first outlet closure at its station and divert subsequent discharge through the second outlet thereof upon timing out of the associated timing means at its maximum time setting; a second series of outlet closure operating means, each connected to a respective one of said second series of timing means, and each operable to close the second outlet closure at its station and divert subsequent discharge through the auxiliary outlet thereof upon timing out of the associated timing means at its maximum time setting; a corresponding series of sensing means, the sensing means at each station connected to said first and second timing means for said station, for limiting operation of said timing means and outlet closure operating means to periods in which a sufiicient supply of material is available to permit discharge at a relatively constant rate; and means for resetting all of said timing means of each series upon timing out of the last timing means of the series at its minimum time set-ting.

13. A control system for a Water scalping tank, or like classifying apparatus for granular material, having a series of outlet stations each including a first outlet, a second outlet, and an auxiliary outlet, each outlet having an outlet closure, said control system comprising: a first and a second series of individual independently settable timing means, one of said series for each station, for establishing maximum and minimum discharge times for respective ones of said first and second outlets; a first series of outlet closure operating means, each connected to a respective one of said first series of timing means, and each operable to close the first outlet closure at its station and divert subsequent discharge through the second outlet thereof upon timing out of the associated timing means at its maximum time setting; a second series of outlet closure operating means, each connected to a respective one of said second series of timing means, and each operable to close the second outlet closure at its station and divert subsequent discharge through the auxiliary outlet thereof upon timing out or" the associated timing means at its maximum time setting; and means for resetting all of said timing means of each series upon timing out of the last timing means of the series at its minimum time setting; and ratio control means, connected to all of said second series timing means, for actuating said second series timing means and said second series closure operating means to discharge material through said second outlets in accordance with a predetermined limited duty cycle during intervals when material is also being discharged through said first outlets.

14. A control system for a Water scalping tank, or like classifying apparatus for granular material, havinga series of outlet stations each including a first outlet, 2.-

second outlet, an an auxiliary outlet, each outlet having an outlet closure, said control system comprising: a first and a second series of individual independently settable' timing means, one of each series for each station, for

respective one of said second series of timing means, and I each operable to close the second outlet closure at its station and divert subsequent discharge through the auxiliary outlet thereof upon timing out of the associated timing means at its maximum time setting; a corresponding series of sensing means, the sensing means at each station being connected to said first and second timing 7 means for said station, for limting operation of said timing means and outlet closure operating means to periods in which a sufiicient supply of material is available to permit discharge at a relatively constant rate; means for resetting all of said timing means of each series upon timing out of the last timing means of the series at its minimum time setting; and ratio control means, con nected to all of said second series timing means, for actuating said second series timing means and said second series closure operating means to discharge material 7 through said second outlets in accordance with a predetermined limited duty cycle during intervals when material is also being discharged through said first outlets.

IS. A control'system for a Water scalping tank, or like apparatus for classifying material, having a series of outlet stations at which different classes of material accumulate at varying rates, each outlet station including at least one main outlet and an auxiliary outlet, each outlet having an outlet closure actuated by an outlet closure actuator, said control system comprising:

means connected to said outlet closure actuators for inhibiting opening of both outlet closures at each station until sufiicient material accumulates to permit discharge thereof at a relatively constant rate;

a series of individual settable measuring means, one

for each station, for measurins the discharge of material through respective ones of said main outlets;

a corresponding series of outlet closure control means, each'connected to the measuring means and to the outlet actuators at a respective outlet station and operable to close the main outlet closure at that station and divert subsequent discharge through the auxiliary outlet thereof in response to measurement by the associated measuring means of a preset discharge through the main outlet at said station;

and automatic reset means, coupled to all of said measuring means, for resetting all of said measuring means upon completion of the preset discharge through the main outlet of the last of said stations to re-initiate discharge through said main outlets.

16. A control system for a water scalping tank or like apparatus for classifying material, according to claim in Which each said measuringmeans comprisesan independently settable timing device for cumulatively measuring the discharge time of material through the associated main outlet, 

1. A CONTROL SYSTEM FOR A WATER SCALPING TANK OR LIKE CLASSIFYING APPARATUS FOR GRANULAR MATERIAL HAVING A SERIES OF OUTLET STATIONS EACH INCLUDING FIRST, SECOND AND THIRD OUTLETS, SAID CONTROL SYSTEM COMPRISING: A FIRST, A SECOND, AND A THIRD SERIES OF OUTLET OPERATING MEANS, ONE OF EACH FOR EACH OUTLET STATION, FOR OPENING AND CLOSING SAID FIRST, SECOND AND THIRD OUTLETS, RESPECTIVELY; A FIRST AND A SECOND SERIES OF TIMING MEANS INDIVIDUALLY CONNECTED TO THE FIRST AND SECOND OUTLET OPERATING MEANS, RESPECTIVELY, AT THE RESPECTIVE OUTLETS STATIONS, FOR MEASURING THE DISCHARGE TIME OF MATERIAL THROUGH THE RESPECTIVE ONES OF SAID FIRST AND SECOND OUTLETS, EACH OF SAID TIMING MEANS BEING ACTUATABLE FROM A FIRST OPERATING CONDITION TO A SECOND OPERATING CONDITION, UPON DISCHARGE OF A PREDETERMINED AMOUNT OF MATERIAL THROUGH THE ASSOCIATED ONE OF SAID FIRST OUTLETS, ACTUATION OF EACH TIMING MEANS BEING EFFECTIVE TO CLOSE THE CORRESPONDING OUTLET AT EACH STATION AND DIVERT SUBSEQUENT DISCHARGE TO THE OTHER OUTLETS AT THE SAME STATION; AND MEANS CONNECTED TO THE THIRD SERIES OF OUTLET OPERATING MEANS, FOR PREVENTING DISCHARGE THROUGH ANY OF SAID THIRD OUTLETS EXCEPT WHEN BOTH THE FIRST AND SECOND OUTLETS AT THE SAME STATION HAVE BEEN CLOSED BY THE ASSOCIATED TIMING MEANS. 